An optical disc capable of recording large volume of data with high density has been developed to further make the capacity higher by forming the recording layer into a multi-layer structure. For example, the approach has been taken to use four layers each with standard recording density of 25 GB/layer and three layers each with high recording density of 33 GB/layer for forming the blue ray disc (BD). The use of the optical disc with different recording formats including the recording density requires the optical disc apparatus for performing recording/playback in accordance with the identified format.
Patent Document 1 discloses the related technology as the structure for selecting the optical system (numerical aperture, NA) in accordance with the disc type, and further changing property of the signal processing system in association with the selection. In the case where the single disc has plural recording layers each recorded in accordance with a different format, the structure disclosed in Patent Document 2 records the format information of plural recording layers in the lead-in area so as to identify each format of the respective recording layers.